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authorChris Metcalf <cmetcalf@mellanox.com>2016-07-14 22:48:14 +0200
committerWill Deacon <will.deacon@arm.com>2016-08-22 11:00:48 +0200
commit421dd6fa6709ebee4f888ed89da5c103c77caee1 (patch)
tree2ee670bc18f5fbe691906340c0a54b42f7f2635a /arch/arm64/kernel/entry.S
parentarm64: hibernate: reduce TLB maintenance scope (diff)
downloadlinux-421dd6fa6709ebee4f888ed89da5c103c77caee1.tar.xz
linux-421dd6fa6709ebee4f888ed89da5c103c77caee1.zip
arm64: factor work_pending state machine to C
Currently ret_fast_syscall, work_pending, and ret_to_user form an ad-hoc state machine that can be difficult to reason about due to duplicated code and a large number of branch targets. This patch factors the common logic out into the existing do_notify_resume function, converting the code to C in the process, making the code more legible. This patch tries to closely mirror the existing behaviour while using the usual C control flow primitives. As local_irq_{disable,enable} may be instrumented, we balance exception entry (where we will almost most likely enable IRQs) with a call to trace_hardirqs_on just before the return to userspace. Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
-rw-r--r--arch/arm64/kernel/entry.S12
1 files changed, 4 insertions, 8 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 441420ca7d08..6a64182822e5 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -707,18 +707,13 @@ ret_fast_syscall_trace:
* Ok, we need to do extra processing, enter the slow path.
*/
work_pending:
- tbnz x1, #TIF_NEED_RESCHED, work_resched
- /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */
mov x0, sp // 'regs'
- enable_irq // enable interrupts for do_notify_resume()
bl do_notify_resume
- b ret_to_user
-work_resched:
#ifdef CONFIG_TRACE_IRQFLAGS
- bl trace_hardirqs_off // the IRQs are off here, inform the tracing code
+ bl trace_hardirqs_on // enabled while in userspace
#endif
- bl schedule
-
+ ldr x1, [tsk, #TI_FLAGS] // re-check for single-step
+ b finish_ret_to_user
/*
* "slow" syscall return path.
*/
@@ -727,6 +722,7 @@ ret_to_user:
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
+finish_ret_to_user:
enable_step_tsk x1, x2
kernel_exit 0
ENDPROC(ret_to_user)